With the development of power systems, novel powers have been increasing into the systems or the subnets connect with each other. This increases the capacity of short circuit of systems. It leads some fault positions current exceed the interrupting capacity of the switches. Generally, the switch is very dear, and renew a switch will take much time; therefore, people always adopt various technical measures to limit the fault current.
The self-cooled thyristor valve which is used for ultra-high voltage fault current limiter (FCL) is a key device in such as resonance FCL, rapid switch FCL, complex FCL and so on. It is mainly used as a rapid switch. FIG. 1 is a resonance FCL working principle diagram. The resonance FCL includes reactor L, capacitor C, and rapid bypass switch K (can adopt thyristor valve, spark gap, rapid mechanical switch and their composition switch). The value of inductive reactance of reactor L is same to that of the capacitive reactance of capacitor C. Under normal working condition, the switch K is off (thyristor valve is blocking), while capacitor C and reactor L are both under the series resonance state, resulting in zero impedance. When a fault current is detected, the switch K will shut down rapid (the thyristor will conduct rapidly), the capacitor C will be bypassed which is equal to connect the reactor L with the electric circuit. So the current will be limited.
Now there have been some flexible thyristors used for alternating current transmission device and direct current transmission device. But in normal condition, a set of complex and expensive cooling system are need due to the long period operation of the thyristor. This reduces the reliability of the entire device. While it needn't resistant long period fault current in abnormal condition, the thyristor must be protected reliably. The present invention meets the requirement of the FCL long period operation under the fault current circumstance, and also improves the operation reliability of entire device because adopts a self-cooled design.